@mixin themify($themes: $themes) {
  @each $theme-name, $map in $themes {
    // & 表示父级元素
    // !global 表示覆盖原来的
    .theme-#{$theme-name} & {
      $theme-map: () !global;
      // 循环合并键值对
      @each $key, $value in $map {
        $theme-map: map-merge($theme-map, ($key: $value)) !global;
      }
      // 表示包含 下面函数 themed()
      @content;

      $theme-map: null !global;
    }
  }
}

@function themed($key) {
  @return map-get($theme-map, $key);
}